One can imagine all kinds of confounding effects, where some other thing makes someone more likely to use porn, and also is (or causes) something else that is good or bad. And the confounding effects are likely to be different in different subpopulations (e.g. young university kids; people who were raised religious and might not be anymore; people in relationships, some of which are going better than others; old people, some of whom are losing their sex drive). So I would put very little trust in any study that didn't involve a randomized intervention. (Which isn't a guarantee of quality—it's only one dimension.) And I think there are plenty of people making claims based on ... well, let's just say their standards for empirical rigor are much lower than mine.
Wiki has an article, which is somewhat interesting to look through. This is a bit hilarious coming after the above:
Studies have looked into both negative effects of pornography as well as potential benefits or positive effects of pornography. A large percentage of studies suffer from methodological issues. In one meta-study by researchers at Middlesex University in England, over 40,000 papers and articles were submitted to the team for review: 276 or 0.69% were suitable for consideration due to the low quality of research within the field.
It could be worth looking into those 276, but I'm not going to do so before posting this comment. (Also I wouldn't be surprised if many of those were bad for reasons the researchers didn't catch.) So, um, I think we're left with armchair theorizing and amateur observation. Let's see.
Ways it could go wrong:
- There are apparently people who get addicted to porn, so maybe it's harmful for them. On the other hand, I think people who get addicted to things often have bad stuff happening in their life already. On the first hand, even if the addiction is caused by bad stuff, it's possible that the addictive behavior makes the situation worse. On the second hand, if you were going to be addicted to something, porn is probably way less bad than, say, drugs or gambling.
- Obviously, porn has its realistic and its unrealistic elements, and people who can't tell the difference and don't know it are likely to do ill-advised things.
- For some, the usage of porn has baggage because of an upbringing that thought it (or perhaps masturbation or sex more generally) was shameful, or because other people in their life have opinions about their porn usage, or it connects to relationship problems (e.g. the partners have differing sex drives, or one wants a type of sex the other is unwilling to do, and uses masturbation with porn to compensate). Recommendations there would be situation-specific, although in general I'd say these situations already have a conflict, and the other option (i.e. abstaining from porn, or masturbation in general) may carry its own downsides (frustration, resentment) and isn't necessarily better.
- I've seen claims that some people get bored with "vanilla" porn, check out something a little spicier, get bored, etc., and end up in pretty extreme places. I'm sure this has happened. I don't think it's common. I also suspect that those people had an underlying tendency and many of them would have arrived at similar places via in-person sex, if their environment made this easy (and would have been frustrated, and done who knows what else, if their environment did not).
Ways it could go well:
- Obviously, people find it pleasurable or otherwise rewarding.
- If one's sex drive would otherwise lead one to do unsafe, immoral, or otherwise bad things, this may be a better alternative. (To some extent one can say this about masturbation regardless of whether it involves porn.)
- If one wants to expand the range of, say, body types or demographics one is interested in, porn is an easy way to explore that.
There is plenty of speculation about long-term effects, habit forming, and so on. (I personally look out for the possibility of becoming dependent on porn, and make a point of masturbating using only my imagination reasonably frequently.) I don't think there are large effects that reliably happen, otherwise I'd probably have heard about it. (There's a whole "No Fap" movement that some subscribe to. I think some people claim it improves their motivation / energy.) Probably, if there are such effects, they affect some people much more than others.
Overall, I'd say "seems probably harmless; it's probably worth having some awareness of failure modes and paying attention to yourself, but beyond that, do what thou wilt".
I don't think this is a good metric. It is very plausible that porn is net bad, but living under the type of govermnment that would outlaw it is worse. In which case your best bet would be to support its legality but avoid it yourself.
I'm not saying that IS the case, but it certainly could be. I definitely think there are plenty of things that are net-negative to society but nowhere near bad enough to outlaw.